Foam-bead-crete

[pwschiller]

Has anyone used a lightweight concrete mixture made with recycled polystyrene beads as insulation? I read about it on builditsolar.com, but haven't been able to find out what the ideal concrete mix and concrete to foam ratio would be. There are companies that make such a product pre-mixed in dry form, which includes a suspension agent so that the foam beads don't all float to the top, but the mixture is proprietary. I guess I could ask the concrete company to add whatever suspension agent they use for their normal lightweight concrete mix.

I am considering putting my underground PEX lines inside of two 3" conduits with 3/4" of pipe insulation around the PEX. I have hundreds of feet of the conduit that I will probably never use all of. Around the two 3" conduits would be a minimum of 6" of foam-bead-crete mixture. I read all of the postings in the "Underground lines - not the place to skimp!" sticky, but I like the idea of being able to replace the PEX lines in the future if needed. The underground run will be about 100' each way, with a portion of it under the slap of my to-be-built boiler/workshop building.

I already have about 10 cubic yards of recycled polystyrene beads stashed in my barn. I just don't want to order a yard of concrete, start dumping my foam beads into the concrete mixer/truck and end up with a big mess. If I don't attempt the foam-bead-crete mixture, I'll probably spray foam my underground lines and then use the foam beads to insulate my storage tanks.

 

[heaterman]

I think the purpose of the foam beads is not so much to provide insulating value as it is to reduce weight per cubic foot. Might help a wee bit but I have to think all the space between the beads would remain as conductive as normal concrete. Sounds kinda like the R-70 paint i read about a while ago.

 

[pwschiller]

This is the best reference I have found for it, and the one that gave me the idea for it in the first place: http://www.builditsolar.com/Projects/SpaceHeating/BeadFoamCrete.htm

It is a bit vague on exactly what the concrete mix should be, other than 1 part concrete to 9 parts foam. I assume that would have to be by volume. It claims an R-value of about 1.7, although that would clearly change as you change the proportions in the mix.

I would need enough of the mixture that I would need to mix it in a concrete mixing truck. I'm having trouble imagining how you would get such a large volume of statically charged foam beads into the mixing drum opening once the concrete truck arrives, without just making a huge mess. The guy who manages the concrete operations at the local plant is willing to let me try it out, but I would like to hear from someone else who has worked with this stuff.

 

[Willman]

Using conduit for chases is the way to go. Nothing wrong with providing "serviceability"I would use the highest grade pipe insulation, also see if it can be bought in longer lengths. Spray foam is the way to go though. Not certain what the beads R value would work out to be. Box in your tanks and do a pour.

Will

 

[Frozen Canuck]

I would avoid trying this one out just to see if it works for the following reasons: Just to name a few!

Styrofoam "beads" will be smooth & therefore take strength away from the concrete mix rather than add to it or have a neutral effect on psi strength of concrete, poor bond with any aggregate = less strength. If a large amount of foam is added you may wind up with a product no stronger than compressed earth. If so I suggest staying with the earth.
You will gain little or no R value from beads in concrete as it is not as described continuos insulation, only intermittent & therefore usless.
The concrete truck(s) will likely be contaminated with foam beads that will remain in the mixer after your job is done & contaminate future loads resulting in them being refused at any commercial/industrial job until the contaminate has been removed. I don't think the manager has thought it through past your experiment, as any engineered job has a rep on site during structural pours & those beads will be noticed. Removing them involves a jack hammer, a sandblaster & many hours of labor, unless you have several hundred gallons of water on site & they are willng to float out all the foam before it bonds to the inside of the drum.
Have you determined whether the beads are compatible with the concrete mix? If they react they will likely melt & possibly off gas. Not a good thing.
Have you determined whether the beads will react when heated? If you intend to use them as insulation around your storage tanks, again they could melt & off gas depending on what type of foam they are.

Honestly I see no upside to this, just lots of potential downside on expensive load(s) of concrete.

If it were me I would pass, let someone else be the canary in the coalmine.

 

[Duetech]

Unless the concrete/foambead mix is in a water proof casing it will absorb moisture and become a thermal conductor. Infra red is one way heat is lost from your lines as well. Thick spray foam is rather successful in IR transfer though not perfect. There are rolled IR reflective products that claim 90% containment of IR that should go around your conduits before installing your conduit into the ground with either foam or concrete if you want a real good thermal barrier. Foam is a "way" better insulator than the concrete mix though.

 

[pwschiller]

I find it a rather irritating when people don't fully read your original posting or bother to read the links provided, but then try to shoot holes through everything. I appreciate constructive feedback - things to consider that perhaps I haven't yet, but what I was really looking for was someone who has worked with foam-bead-crete.

Styrofoam "beads" will be smooth & therefore take strength away from the concrete mix rather than add to it or have a neutral effect on psi strength of concrete, poor bond with any aggregate = less strength. If a large amount of foam is added you may wind up with a product no stronger than compressed earth.

I'm not looking for high strength. It's a means to hold the foam beads together and provide some compressive strength. There's actually a company that makes ICFs out of foam-bead-crete: http://www.rastra.com/[/quote]

You will gain little or no R value from beads in concrete as it is not as described continuos insulation, only intermittent & therefore usless.

Again, the author of the first reference that I posted claims an R-value of 1.7 per inch and Rasta makes similar claims. I would be using a high volume of the product to further insulate sealed conduits containing already insulated PEX. I also plan on wrapping the bead-crete with plastic and all of that will be sitting on crushed stone for drainage.

I don't think the manager has thought it through past your experiment...

If you had read the link that I had provided you would have seen that this has been done before. I asked for feedback from people who have worked with foam-bead-crete.

Have you determined whether the beads are compatible with the concrete mix? If they react they will likely melt & possibly off gas. Not a good thing.

It's expanded polystyrene beads. Perhaps you've heard it referred to as Styrofoam? It's used in all sorts of building applications. In fact here's a company that makes ICFs out of EPS, which would then be in direct contact with concrete: http://www.arxx.com/

Have you determined whether the beads will react when heated? If you intend to use them as insulation around your storage tanks, again they could melt & off gas depending on what type of foam they are.

Have you ever had a Styrofoam coffee cup melt in your hand? I haven't.

 

[sdrobertson]

When I was researching insulation for my storage tanks, I really wanted to go with Styrofoam beads that are used here for block filler as they are cheap and have a high R-value. I made several calls to manufactures and what I came up with is that they will not withstand constant temps of 180 degrees. I did use several feet of them at the very bottom of my storage and then used dense pack cellulose for the top 3/4 of the storage. I'd be concerned about the foam melting at about 170ish as you want this to last for many, many years.

 

[pwschiller]

When I was researching insulation for my storage tanks, I really wanted to go with Styrofoam beads that are used here for block filler as they are cheap and have a high R-value. I made several calls to manufactures and what I came up with is that they will not withstand constant temps of 180 degrees. I did use several feet of them at the very bottom of my storage and then used dense pack cellulose for the top 3/4 of the storage. I'd be concerned about the foam melting at about 170ish as you want this to last for many, many years.

Thanks for that info.

I did a little more research after reading your posting. EPS has a melting temp of 240 C (464 F), a glass transition temp of 95 C (203 F), a continuous service temp of 165 F, and an intermittent service temp of 180 F.

According to Wiki, "The liquid-glass transition (or glass transition for short) is the reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle state into a molten or rubber-like state." One of the key words there is "reversible".

One definition that I read for continuous service temp was: "The highest temperature at which a material can function for an extended period of time without failing." I guess the question is, what is meant by failing? If it just means the point at which strength is compromised, that may not be relevant when you're talking about loose fill foam beads used as insulation. If on the other hand it means that the foam beads start to disintegrate due to a combination of heat and oxidation, that's an issue.

So, I'm not sure what to make of all of that. Perhaps the easiest (although not the cheapest) solution would be to first spray the tanks with a thin layer (1" or so) of urethane/isocyanurate foam and then use the foam beads to fill in the rest of the tank enclosure. If the foam beads were to shrink or settle slightly over time it would be easy enough to add more to the tank enclosure.

 

[leaddog]

When I was researching insulation for my storage tanks, I really wanted to go with Styrofoam beads that are used here for block filler as they are cheap and have a high R-value. I made several calls to manufactures and what I came up with is that they will not withstand constant temps of 180 degrees. I did use several feet of them at the very bottom of my storage and then used dense pack cellulose for the top 3/4 of the storage. I'd be concerned about the foam melting at about 170ish as you want this to last for many, many years.

Thanks for that info.

I did a little more research after reading your posting. EPS has a melting temp of 240 C (464 F), a glass transition temp of 95 C (203 F), a continuous service temp of 165 F, and an intermittent service temp of 180 F.

According to Wiki, "The liquid-glass transition (or glass transition for short) is the reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle state into a molten or rubber-like state." One of the key words there is "reversible".

One definition that I read for continuous service temp was: "The highest temperature at which a material can function for an extended period of time without failing." I guess the question is, what is meant by failing? If it just means the point at which strength is compromised, that may not be relevant when you're talking about loose fill foam beads used as insulation. If on the other hand it means that the foam beads start to disintegrate due to a combination of heat and oxidation, that's an issue.

So, I'm not sure what to make of all of that. Perhaps the easiest (although not the cheapest) solution would be to first spray the tanks with a thin layer (1" or so) of urethane/isocyanurate foam and then use the foam beads to fill in the rest of the tank enclosure. If the foam beads were to shrink or settle slightly over time it would be easy enough to add more to the tank enclosure.

I ran some hot lines thru stryrofoam and after time the foam tended to shrink away from the lines so there was a gap. The lines went up to maybe 200* a few times. The beads could be used if you have a foam base keeping the heat down but I would not use it any place that the temp got over 160* ever. There is better insulation for that. Also I would wonder about water absorbtion as some syrofoam will absorb water if in a contained area for long times. If I had that much beads I would think about covering the tank to lower the temp and then using the beads, they do tend to fill cavities very well. The other down side in using them is if you ever have to work on the tanks and open up the cavity beads go EVERY where and stick to every thing and just a little wind and it's worse than a snow storm.
leaddog

 

[jimbom]

Normally, an engineer designing Portland cement mixes prepares a few small samples covering a range of proportions using the materials at hand. These small cured samples can be placed in simulated service and checked for stability, moisture adsorption, etc. ACI(American Concrete Institute) has design manuals and information on insulating concrete. The design process will teach you everything you need to know about mixing, placing, and curing your insulating concrete.

Personally, I like to start with the quality of my aggregate. If it passes, I design the mix. In this case, I would submerge the polystyrene and check for water adsorption plus the resultant R-value. If it is satisfactory, then I would move on to mix design.

 

[pwschiller]

The other down side in using them is if you ever have to work on the tanks and open up the cavity beads go EVERY where and stick to every thing and just a little wind and it's worse than a snow storm.
leaddog

If I use them for this purpose, I think that I will use foam sheathing and spray foam to create two compartments within the tank enclosure. One narrow vertical channel that will allow easy access to all of the tank connections and thermowells and another that will surround about 80% of the tanks with the foam beads. In the area where all of the connections and thermowells are located I'll probably insulate with Roxul batts and have easy to remove access hatches.

 

[pwschiller]

Normally, an engineer designing Portland cement mixes prepares a few small samples covering a range of proportions using the materials at hand. These small cured samples can be placed in simulated service and checked for stability, moisture adsorption, etc. ACI(American Concrete Institute) has design manuals and information on insulating concrete. The design process will teach you everything you need to know about mixing, placing, and curing your insulating concrete.

Personally, I like to start with the quality of my aggregate. If it passes, I design the mix. In this case, I would submerge the polystyrene and check for water adsorption plus the resultant R-value. If it is satisfactory, then I would move on to mix design.

That's an excellent suggestion that I make a couple of small test batches. Maybe when it warms up a bit - and stops snowing.

I'll also see if my local concrete supplier has those ACI manuals. You would think so.

Thanks.

 

[NYEDGE]

Normally, an engineer designing Portland cement mixes prepares a few small samples covering a range of proportions using the materials at hand. These small cured samples can be placed in simulated service and checked for stability, moisture adsorption, etc. ACI(American Concrete Institute) has design manuals and information on insulating concrete. The design process will teach you everything you need to know about mixing, placing, and curing your insulating concrete.

Personally, I like to start with the quality of my aggregate. If it passes, I design the mix. In this case, I would submerge the polystyrene and check for water adsorption plus the resultant R-value. If it is satisfactory, then I would move on to mix design.

That's an excellent suggestion that I make a couple of small test batches. Maybe when it warms up a bit - and stops snowing.

I'll also see if my local concrete supplier has those ACI manuals. You would think so.

Thanks.

I agree with JimboM.
I would do several test batches and then you can determine if the results are to your liking.
You can either mix your own concrete from scratch with cement, sand, and gravel, or sometimes the concrete plant has 1/2 yard or so coming back in the truck and they may be willing to dump it quickly at your site if your around. Another problem will be trying to mix the pellets into the concrete so that they are incorporated in order to achieve a good consistancy throughout the mix.
Wetting down the pellets with water should help reduce the static in them while you work with them.

I stamp allot of concrete, stain concrete, and create polished concrete counter tops. The key to figuring out if this is the way to go is make several samples and document you recipe for each sample so that you can duplicate it on a larger scale when the time comes. Don't forget to make a couple of control samples (just concrete) so that you can compare your modified mixes with the real deal. I understand that you are more interested in the insulating properties of the concrete than the strength of it, but make sure that it holds up to back filling and any vehicle loads that may on top of the lines. Once your modified samples and control samples are ready you can test them at the same time with a constant heat source on one side and shoot the other side with an infra red gun to see the heat transfer.

Good luck, and don't forget to let us know your progress. I for one am always interested in these little experiments.

 

[DaveBP]

Pete, if you are interested in using this mix primarily as an insulating material, have you thought about using a paste coating of cement and water to bind the beads together but not add any more mass (read thermal conductor) than necessary? No crushed stone. Maybe fine sand like twice-screened mortar sand.

Almost anything you do will not be impervioust to water and any water that gets into the stuff will reduce the insulation value of it.

 

[Floydian]

Hi Pete, interesting idea.

I agree with this:

Almost anything you do will not be impervioust to water and any water that gets into the stuff will reduce the insulation value of it.

Also, its hard for me to imagine that cracks wouldn't form somewhere in that 100' run, but I've been wrong plenty. Cracks+water could equal BIG heat loss.

I wonder about skipping the 3/4" pipe insulation, sleeve the pex in the conduit and spray foam the whole shebang with 3+ inches of
2 lb closed cell urethane. Shifting the cost of 200' of pipe insulation towards spray foam may be well worth it. Certainly worth getting a couple of quotes I'd think.

If I recall correctly you are looking at a lambda boiler, right? A top of the line boiler deserves the best underground line installation possible which IMHO is spray foam.

Good luck,
Noah

 

[bpirger]

Conduit is great to be able to replace. Just make sure they won't ever be wet, filled with water, etc. That's a whole lot of heat to have to keep dumping. Presuambly if the installation goes ideally, they will be watertight, PVC septic lines obviously are done all the time. You may want to slope the lines and intentionally leave an end open just to make sure. I know i have water in one of my buried 4" lines, that I didn't intend....

I buried microflex to replace my 1" lines inside pipe insulation, inside a 4" conduit. I tried to place 2" of extruded polystyrene around the conduit...easier said then done. And when I dug some of it up, the insulation was soaked through and very heavy...no insulation there. I know I'm losing about 25% of my heat through this short 30' (x2 = 60') run of these lines. Looking forward to getting a chance to switch over to the microflex.

 

[pwschiller]

Conduit is great to be able to replace. Just make sure they won't ever be wet, filled with water, etc. That's a whole lot of heat to have to keep dumping. Presuambly if the installation goes ideally, they will be watertight, PVC septic lines obviously are done all the time. You may want to slope the lines and intentionally leave an end open just to make sure.

It's 3" schedule 40 conduit. My workshop will be at a slightly higher elevation than my house, so I was planning on having the conduit pitched slightly the whole way, just like you do with waste lines. I had to glue up over a mile of conduit when I built my house (3 runs x 1800'). It should be water tight if done right. If not, I'll find out when it drains into my basement.

 

[pwschiller]

Pete, if you are interested in using this mix primarily as an insulating material, have you thought about using a paste coating of cement and water to bind the beads together but not add any more mass (read thermal conductor) than necessary? No crushed stone. Maybe fine sand like twice-screened mortar sand.

That's what I was thinking, that a sand mix with a high portland cement content would probably be best. I have no idea what they use for suspension/wetting agents when they mix lightweight concrete (with perlite?). I would think that it would have similar issues to the foam-crete, although the foam beads may be even more resistant to wetting. I'll try to find out from the concrete guy what goes into their lightweight mixes.

 

[pwschiller]

Also, its hard for me to imagine that cracks wouldn't form somewhere in that 100' run, but I've been wrong plenty. Cracks+water could equal BIG heat loss.

I don't think that cracks in the foam-crete would be much of an issue, since the PEX will be inside of a dry (if done properly) conduit. It would only affect a tiny cross section of the 100' run. Also, I was planning on putting this all below the frostline.

The big issue would be if the foam-crete becomes effectively waterlogged over time, so that all of it becomes a poor insulator. Putting down a bed of crushed stone under all of it should help, but is no guaranty. Unless I can find some existing data I may just have to make some test samples to see how they perform.

Maybe I should start a poll. If you had 10 cubic yards of polystyrene foam beads, would you:
1) use it to insulate your storage tanks
2) test out the foam-crete idea
3) start making bean bag chairs

 

[bigburner]

The conduit isn't a bad idea. We had a pallet of 20 ft - 4inchers around here, it's amazing what you can find to do with it. As far as the beads. Watch the weather and when the man says 20 to 25 MPH wind take the beads and set them free. That stuff is only good in it's heaviest density, not in a bag. If you use it loose around your tanks you will have beads floating around there forever. Closed cell foam on the conduit and then armorflex on the pex.

 

[benjamin]

Apparently I have as much experience with foam beads as anyone else, and that's not much. I've fooled around with foam and/or sawdust crete and gave up all hope as a building material.

The article mentioned a nine to one mix with cement slurry, and then a cement pea gravel mix also, either one is self explanatory, they don't mention a suspension agent so I assume they just mix it dry enough that it won't segregate. I'm sure foamcrete works fine for the author's intended use in Annualized Geo Solar which is storing heat in earth under the building and reducing heat loss by sheer distance and low temp gradient. This is a very different use than insulating boiler lines run a significant distance between buildings. The r value of 1.7 is pretty mediocre compared to the alternatives. A high r value is especially important because of the small diameter/surface area of the pipes, if the heat can be held close to the pipe then it won't expand the conduction area like it will with a greater thickness of insulation of a lower r value per inch.

 

[pwschiller]

Apparently I have as much experience with foam beads as anyone else, and that's not much. I've fooled around with foam and/or sawdust crete and gave up all hope as a building material.

Is that because you haven't gotten the strength vs. insulating value you were hoping for or because it was a horrible mess that just didn't seem like it was worth the bother?

The r value of 1.7 is pretty mediocre compared to the alternatives.

It is, but it's not the only source of insulation. Around the PEX would be 3/4" of elastomeric pipe insulation which is about R-5. Then there's an air space between most of that and the schedule 40 conduit. Then if there's a minimum of 6" of foam-crete around the conduits, that would be another R-10 (if it's actually R-1.7/inch). All of that would be below the frost line and be carrying approximately 150 F water. That's really not bad at all if the foam-crete is able to maintain its R-value long-term.

I already have hundreds of feet of extra conduit (that would likely go unused) and the foam beads were free. The pipe insulation is about $1.40 per foot. The concrete will be under $200. So my total cost for insulating my two 100' underground PEX lines would be under $500, not including the crushed stone that would go in the trench for drainage. I like the idea of being able to replace the PEX in the future if I had to; especially the section that will pass under the slab of my boiler/workshop building.

 

[Tennman]

I'm sorry, I'm short on time but will give my brief 2 cents. I bought 300' sections of 1.25 PEX to assure there would be no joints underground. The projected lifetime of PEX is 200 years. Google Pex lifespan. The shortest is 50 years which still puts it beyond being my problem. So, although it sounds attractive to be able to replace the pex, in a practical sense that should never happen even if placed directly in the dirt... much less if encased in an insulator. Also I'm sure the lifetime factors in fatigue from much higher pressures that what we use (our boiler autofill is set at 12 psi).

From a thermal efficiency standpoint, thermal energy moves by three methods: conduction (material touching material), convection (gases in proximity to something warmer than the surrounding), and radiant (infrared energy irradiating from the hotter surface). With the pipe in a pipe you have all three going on which translates into a thermal energy "leakage" big time. Although attractive, the idea of replacement, the odds in the lifetime of everyone reading this is very, very remote. Every example of high efficiency insulator attempts to stop all three heat transfer methods as close to the energy source as possible. As I understand the concrete concept you will also be creating a very large thermal mass which will certainly be the same temp as the ground which in a thermal sense will create a very large energy sucking sound.

My point is that in an attempt to prevent the least likely scenario, you are creating one of low efficiency.

 

[benjamin]

I agree with everything Tennman said. The key is to hold the heat as close to the pipe as possible, because every inch that the heat travels gives it that much more surface area to travel through. I plan to use a box of extruded foam with expanding foam inside around the pipes when/if I run lines to the shop. Reducing the heat loss if far more important in my mind than being able to replace the line.

I was looking for a material to use as a monolithic building material and it just didn't make sense, insulation is insulation and framing is framing. I think foam crete could work just fine for some uses. I think what I did and what the article described is mixing up a cement/water slurry and mixing in nine parts foam, the cement doesn't have to fill all the gaps, though that would help stop convection in your case. They also mentioned a pea gravel mix, and I'm not sure what the reason for the pea gravel was, unless it was to facilitate mixing the cement slurry.